>Article: 267 of bionet.plants
>From: rjsalvad at IASTATE.EDU (Ricardo J Salvador)
>Newsgroups: bionet.plants
>Subject: Barbara McClintock Dies
>Message-ID: <1992Sep3.180229 at IASTATE.EDU>
>Date: 3 Sep 92 23:02:29 GMT
>Received this morning the sad news that Dr. Barbara McClintock has died.
>This unquestionably marks the end of an era, and I thought it should not
>go without remark in bionet.plants.
I'd like to except for you a few of Barbara's words that I
fell in love with when I first read them. From her 1984
Nobel Lecture:
"Because I became actively involved in the subject of genetics
only 21 years after the rediscovery, in 1900, of Mendel's
principles of heredity, and at a stage when acceptance of those
principles was not general among biologists, I have had the
pleasure of witnessing and experiencing the excitement created by
revolutionary changes in genetic concepts that have occurred over
the past sixty-odd years. I believe that we are again
experiencing such a revolution. It is altering our concepts of
the genome: its component parts, their organizations, mobilities,
and their modes of operation. Also, we are better able to
integrate activities of nuclear genomes with those of other
components of a cell. Unquestionably, we will emerge from this
revolutionary period with modified views of components of cells
and how they operate, but only however, to await the emergence of
the next revolutionary phase that will again bring startling
changes in concepts.
"The experiment that alerted me ...commenced with the growing of
450 [maize] plants in the summer of 1944, each of which had started its
development with a zygote that had received from each parent a
chromosome with a newly ruptured end of one of it's arms. The
design of the experiment required that each plant be self-
pollinated...to isolate...new mutants that were expected to
appear...
"Some seedling mutants of the type expected did segregate, but
they were overshadowed by totally unexpected bizarre phenotypes.
These segregants were variegated for type and degree of
expression of a gene....
"...Twin sectors appeared in which the patterns of gene
expression in the side-by-side sectors were reciprocals of each
other...
"After observing many such twin sectors, I concluded that
regulation of pattern of gene expression in those instances was
associated with an event occurring at a mitosis in which one
daughter cell had gained something that the other daughter cell
had lost. Believing that I was viewing a basic genetic
phenomenon, all attention was given, thereafter, to determining
just what it was that one cell had gained that the other cell had
lost. These proved to be transposible elements that could
regulate gene expressions in precise ways. Because of this I
called them "controlling elements." Their origins and their
actions were a focus of my research for many years thereafter. It
was their origin that is important for this discussion, and it is
extraordinary. I doubt if this could have been anticipated
before the 1944 experiment. It had to be discovered accidently."
Barabara McClintock
"The Significance of Responses of the Genome to Challange"
Science 226:792-801 1984
And in those last sentences we hear the echo of how thunderstruck
she must have been. If her working hypothesis was correct, she
realized that she was about to become the first person to
investigate an unknown genetic universe. Just as the Newtonian
Universe deceived us about the "real" Quantum Universe, so
Barabara saw that Classical Genetics deceived us about the real
Genomic Genetics.
Steve Modena nmodena at unity.ncsu.edu